I've been operating a Virginia Tech design
solar kiln for a year now, and am curious
about the need to dry lumber below the
ambient EMC if the lumber will be stored
for an appreciable length of time.
In other words, are there any advantages
to drying lumber down to, say, 8% MC when
it will be stored in an unheated building
and acclimate in the 12-14% MC range?
When the lumber is eventually pulled from
the building for use, and handled in a
way that brings the MC down to proper
range - 6-8% - are their any advantages
to initially drying the lumber to that
range, or is drying to the ambient range
of 12-13% adequate?
Gene has mentioned in the past that
properly wrapping 6-8% MC lumber with
4-6 mill plastic will prevent moisture
regain ... but I can see issues with that
approach if pieces are pulled from the
wrapped pile and re-covered numerous times.
The lumber in question is predominantly
4/4 ash
One of the reasons I'm asking is that I've
observed that the solar kiln quickly pulls
the free water from a load, and fairly
quickly works at the bound water from the
30% down to 20% range. At that point,
drying slows, and it seems that getting
the last 6% to 7% out (from the ambient
12-14% range) can take quite a while.
Also - in the winter, reaching the ambient
12-14 range was possible, but it appears
there's not enough heat available to get
down to the 6-8% range(northern PA).
At any rate, the kiln is performing
really well, and I'm just curious if MC
regain to ambient "nullifies" drying the
lumber to low MC's initially, or if there
are warp reducing benefits of initially
drying all the way to 6-8%.